The present invention relates in general to power sources that deliver power to battery-operable devices, and more particularly, to a power delivery unit capable of providing an overload protection while operating an associated system with variable power consumption components and/or operational modes.
For battery-operable devices, among other design constraints related to the size and cost, power consumption and battery life is a significant design constraint. In a mobile environment, for example, performance of a portable device may depend upon the rate of power consumption, translating into the duration of available battery life. Low-power design techniques coupled with other power saving strategies may extend battery life.
However, providing an overload protection while operating an associated system with variable power consumption components and/or operational modes that demand higher power consumption, ensuring extended battery life may be difficult. Even worse, as power consumption increases, the battery life of mobile devices or systems decreases, leading to less attractive consumer products.
Managing power usage by hardware components and/or software applications in a system to keep overall power consumption within limits may be difficult. One reason for this difficulty is that conventional smart battery pack solutions that monitor power at regular intervals fail to quickly take appropriate corrective measures. Therefore, delivering higher performance while still maintaining a good battery life and providing overload protection presents significant challenges especially in mobile platforms.
Typically, a battery may be used in conjunction with an alternating-current/direct-current (AC/DC) adapter to power a system. For example, a conventional notebook computer may include the AC/DC adapter to source power and recharge the battery at the same time with available power from a power outlet. When an over-current protection (OCP) circuit having a trip point detects an over-current condition, the battery may need to be stopped immediately from sourcing current to the notebook computer.
Often high-performance notebook computers comprise a high-performance processor, a large display panel, a large storage-capacity drive (sometimes multiple drives), a compact disk read only memory (CD-ROM), and a digital versatile drive (DVD), each demanding high-power drain from a battery pack having one or more batteries. When fully operational and displaying high-performance applications that may require the processor to perform numerous simultaneous, computations, or operations, such as data reading and writing to the drives, and information displaying at very high luminance level, the total power drain from the battery pack may reach a maximum allowable power envelope. At a low-battery condition, such as when the battery pack is nearing its discharged state, the demand for current from the battery pack may be higher than that of the trip point. This may cause the system to shutdown. This is a problem because valuable data may not have been saved in time before an improper system shutdown occurred.
A hypothetical graph of the battery voltage versus time for a conventional power delivery unit is shown in FIG. 4A. A fully charged battery level 5 for a battery employed in a power delivery system is shown at 12 volts of battery voltage. Likewise, a predetermined battery trip point 7 is indicated at 9 volts of battery voltage. A hypothetical graph of an available voltage 9 is shown with respect to time, because generally the battery voltage decreases over time with usage. In operation, once a system powered by the battery reaches the predetermined battery trip point 7, an unexpected shutdown 12 may result. Without having an ample opportunity to properly power down the system, the unexpected shutdown 12 may result, for example, in catastrophic loss of data.
Thus, better overload protection is desirable in battery operation to reduce system malfunctions.